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126 MEMOIRS OP T H E NATIONAL ACADEMY OF SCIENCES. (c.) REPORT OF MR. C. H ROCKWELL. Prof. E. S. HOLDEN : D E A R S I R : A t the time of the eclipse ot May 6, 1883,1 had a spectroscope with a grating of 14,400 lines to the inch attached to a telescope of 4 inches aperture, using a spectrum of the first order. The grating was so adjusted that the region from a little below E to F was in the field. The slit was narrow, and was not changed; i t was set tangential to the limb of the moon. I did not notice any flash or other phenomena at the time totality commenced. Owing, perhaps, to a passing cloud, I did not see the line K 1474 for the first minute and a half; i t then came somewhat suddenly very distinctly into view, and I was able to follow i t 4' or 5' to the west of the disk of the moon. I repeated this observation a second time with the same result. I saw also two green lines, probably magnesium, each of them brighter and broader than 1474, but much shorter. I saw these two lines each time when I followed 1474 into the corona, but failed to see them when I turned the spectroscope to the north and south sides of the moon. Neither did I see 1474 save on the western side, as already mentioned. As compared with the eclipse of July, 1878, observed at Central City, Colorado, I should say the darkness was less intense on this occasion. I t 18 proper to add, however, that in 1878 I had been reading a chronometer with the aid of a lantern before looking at the corona, while on this occasion I had not used any artificial light for any purpose. Very respectfully, CHAELES H . EOCKWELL. C A R O L I N E I S L A N D , 1th May, 1883. (d.) REPORT OF MR ERASMUS D PRESTON (Published by permission of the Superintendent of the U S Coast and Geodetic Survey ) H O N O L U L U , June 1,1883. Prof. E. S. H O L D E N , Chief United States Eclipse Expedition : D E A R S I R : I have the honor to submit you a report of my observations in connection with the Total Solar Eclipse of May 6, 1883. I n obedience to instructions from Prof. 3\ E. H I L G A R D , Superintendent of the U . S. Coast and Geodetic Survey, I left Washington February 28, and re- ported to you m New York the following day. During the voyage out some preliminary computations were made. A n extended list of stars was selected, suitable for time observations either at Flint or Caroline Island, their factors com- puted and checked,* and pairs of stars were chosen for observations for latitud«j-by the method of equal zenith distances. The instruments furnished by the Coast and Geodetic Survey are as follows: rNS:?RUMENTS. TRANSIT U . S. C. S. Transit No. 2, made by TROUGHTON & SIMMS, of London, to which a delicate level was attached before leaving Washington, for the determination of latitude. The aperture of the telescope is 2J inches with a focal length of 46 inches, and a diagonal eye-piece was used giving a magnifying power of 110. The field of view was 12 minutes of arc, one division of striding level = ⢠The factors A, B, and C for a small list of time stars were computed at Madison by Mr PENNOCK, one of my pupils, and handed to Mr PRESTON for his use.âE. S. H .
SOLAR ECLIPSE, MAY 6,1883. ' 127 0".83âone division of latitude level = 1".75. Correction for pivot inequality, inappreciable. A glass diaphragm was used, having ruled upon i t 13 lines. The equatorial intervals of the three tallies, determined on the island from the transits of ten stars of varying declination, are as follows: Equatorial Intervals, Clamp West. 8. B- -1 -14.50. 2 -12.07. 3 - 9.66. C-- 1 - 4.82. 2 - 2.43. 3 - .01. 4 - f 2.44. 5 - f 4.82. D- - 1 + 9.67. 2 + 12.06. 3 +14.49. Cn«ONOGRAPH. Chronograph No. 8, made by FATJTH & Co., of Washington, was used in all time and pendu- lum observations, and also m recording the observations of contacts during the eclipse. Two cells of the ordinary crow foot gravity battery were in the circuit, which included two observing keys, a sounder, Sidereal chronometer (break-circuit), N E G U S NO. 1589 with condenser and the chronograph. CHBONOMETERS. The two chronometers employed were N E G U S 1589 and H U T T O N , 202 both Sidereal, and both supplied with a break-circuit attachment. The former breaks*every second, omitting the 60thâ the latter breaks every even second and also the 59th. PENDULUM The pendulum swung was the Yard Reversible, P E I E C E NO. 3, made at the Coast and Geodetic Survey Office in 1880. I t is symmetrical in form with reference to the center of figure, and the ratio of the distance of the center of mass from the point of support for heavy end up and heavy end down is as one to three. I t is made of brass with knife edges of steel, and was swung on steel plane. A small reading telescope for observing the amplitude of oscillation of the pendulum. A mercurial barometer. No. 1936, made by G E E E N , of New York, and aneroid, by OASELLA, of London. Four thermometers, by BAUDIN, of Pans. OBSERVATIONS F O E T I M E AND L A T I T U D E . * The pier was finished Sunday afternoon, the 22d of April, but owing to cloudy weather no observations could be made until the evening of the 24th. From that date stars were obtained every evening about 7 o'clock until May 8, inclusive, with the exception of May 3, when wet weather again made i t impossible to observe. Qood sets were also obtained at about 4 o'clock on < the mornings of April 26, 28, 29, 30, May 1, 2, 7 and 8, these morning observations being made in connection with the gravity experiments. The method of equal zenith distances was employed for latitude, and this work was carried on at the same time as the pendulum work, thus filling up the time between the evening and morning time-observations. Latitude was thus observed on six nights, but, owing to difficulty
